1. Field of the Invention
The present invention relates to a liquid crystal display panel, and more particularly to an apparatus and a method for fabricating a liquid crystal display panel that improve a picture quality by improving alignment of an alignment film.
2. Discussion of the Related Art
Generally, a liquid crystal display (LCD) device controls the light transmissivity of liquid crystal cells in accordance with a video signal to display a picture corresponding to the video signal in a liquid crystal display panel. The liquid crystal display device includes a liquid crystal display panel in which the liquid crystal cells are arranged in an active matrix shape, and drives circuitry of the liquid crystal display device. Liquid crystal display devices can be divided into two classes in accordance with the electric field direction when liquid crystal is driven. A twisted nematic (TN) mode where a vertical direction electric field is used and an in-plan switch (IPS) mode where a horizontal direction electric field is used.
The TN mode LCD is driven by a vertical electric field between a pixel electrode and a common electrode, which are arranged to be opposite in the upper substrate. The TN mode LCD has an advantage in that its aperture ratio is large but a disadvantage in that its viewing angle is small. On the other hand, the IPS mode LCD is driven by a horizontal electric field between the pixel electrode and the common electrode, which are arranged in parallel in the lower substrate, and it has an advantage in that its viewing angle is large but a disadvantage in that its aperture ratio is small.
FIG. 1 is a cross-sectional diagram representing a liquid crystal display panel of the TN mode in the related art. Referring to FIG. 1, the TN mode liquid crystal display panel includes an upper array substrate (often referred to as a color filter array substrate) having a black matrix 4, a color filter 6, a common electrode 18, and an upper alignment film 8, which are sequentially formed on an upper substrate 2, a lower array substrate having a thin film transistor (hereinafter, referred to as “TFT”), a pixel electrode 16 and a lower alignment film 38, which are formed on a lower substrate 32, and a liquid crystal injected into the inner space between the upper array substrate and the lower array substrate. On the other hand, the IPS mode liquid crystal display panel have the common electrode 18 formed on the lower substrate 32 and an overcoat layer formed on the color filter 6 of the upper substrate 2, wherein the overcoat layer is to compensate for the stepped difference of the color filter 6.
In the upper array substrate, the black matrix 4 is formed on the upper substrate 2 and corresponds to the areas of gate lines and data lines (not shown) and a TFT area of a lower plate, and it provides a cell area where a color filter 6 is to be formed. The black matrix 4 prevents light leakage and absorbs the external light, thereby increasing contrast. The color filter 6 is formed to extend to the black matrix 4 and the cell area divided by the black matrix 4. The color filter 6 is formed by R, G and B to produce R, G and B colors. A common voltage is supplied to the common electrode to control the movement of the liquid crystal. The spacer 13 keeps a cell gap between an upper array substrate and a lower array substrate.
The TFT includes a gate electrode 9 formed on the lower substrate 32 along with a gate line, semiconductor layers 14 and 47 overlapping the gate electrode 9 and a gate insulating film 44, and source/drain electrodes 40 and 42 formed with a data line (not shown) and the semiconductor layers 14 and 47 in the same process. The TFT supplies a pixel signal to a pixel electrode 16 from the data line in response to a scan signal from the gate line. The pixel electrode 16 is in contact with a drain electrode 42 of the TFT through a passivation film 50, wherein the passivation film is formed of a transparent conductive material with high light transmissivity.
In the related art LCD device, in the chamber within which a designated thin film is formed or in case that it is moved to a separate chamber or a third location to form another thin film, a particle 55 may be frequently formed between the thin films, e.g., the common electrode 18 and an upper alignment film 18 as shown in FIG. 2. A portion of the alignment film 18 corresponding to the particle 55 cannot be uniformly rubbed in a rubbing process, thereby generating a non-uniform alignment area A. The non-uniform alignment area A causes light leakage, thus a spot can appear in the picture as shown in FIG. 3. Generally, a dark spot appears when high gray is produced, and a bright spot appears when low gray is produced. Herein, human eyes are relatively more sensitive to the bright spot than the dark spot, thus a stricter standard is given to the bright spot defect than the dark spot defect when examining the panel. Accordingly, a method is required to prevent the light leakage and the bright spot by repairing the non-uniform alignment area A and to improve the picture quality.